Muscle strength is developed in that the muscle in question is subjected to a physical work with different forms of resistance, which may consist only of the gravity of the body part in question or of external resistance, caused e.g. by a dumbbell, barbell, expander, hydraulic or pneumatic apparatuses. As a continued development of the muscular strength is dependent of progressive increase of the work executed by the muscle, the resistance must be increased from time to time.
During the last century the dumbbell and barbell were the predominate adjustable training apparatuses for the development of maximum muscle strength. But during the last 20 years, the barbell and dumbell have been supplemented with muscle training apparatuses which permit safer and specialized muscle training.
The development of maximum muscle strength and muscle volume is achieved with exercises of short duration at high resistance of a few groups of muscles, which are trained individually. The effect of the training will be most pronounced when all relevant muscular cells or motoric units are stimulated, i.e. via training during isolation of the muscle or muscle group in question.
Such training can be executed statically (without motion) or dynamically (with motion) and isometrically (the muscle has the same length during the work) or concentrically/excentrically (the muscle shortens itself or extends itself during the work).
The art of the work results in development of different types of muscular force, whereas the size of the work resistance decides which quality of the force is to be developed: a high load means increased maximum force, a low load means endurance.
The force which can be developed by an arm or leg depends on its position and the angular orientation of the joint. Training of individual muscle groups must take into account the particular biomechanical working conditions thereof. For training the desired muscular force quality in the entire motion range of the muscle, the work resistance must be adapted to its force potential in each position during the motion.
There are but few training apparatuses fullfiling these training pre-conditions. The resistance unit is often a pneumatic or hydraulic device, which can give an iso-kinetic mode of work (similar speed during the motion), which is sometimes desirable. However, the big drawback with pneumatic and hydraulic training apparatuses is however that the pronounced muscle volume stimulating and energy favourable eccentric motion is not used, and that the speed of the motion can not be varied in relation to a given resistance. The speed of the motion is of big importance as to which muscle fibres are activated, as in all skeleton muscles two types of muscle fibres are present: fast-twitch and slow-twitch. The first mentioned muscle fibres are important for the force generation at rapid and heavy works whereas the later are of importance for slow and endurace characterized work.
Contrary to pneumatic or hydraulic training apparatuses the weight-based machines have the advantage of allowing eccentrical training eccentrically as well as training at different speeds with a certain resistance. The development here has resulted in a more adaptable resistance in the entire range of muscle motion, as certain training apparatuses use a so called cam disc (CAM) as a transmission. The resistance at a given weight load then is modified with the transmission thus that it is is more adapted to the muscle force generation, but this transmission is not adjustable.
The drawback of weight-based muscle training machines or at weight training is that the weights have inertia, which results in varying motion speed in different portions of the motion range. In such a case an optimum of speed and resistance is obtained only in a small range of the motion track, particularly at higher speed.
To an increasing extend, weight training today is combined with training apparatuses based on pneumatic or hydraulic devices. Weight training can be applied with free weights (e.g. barbell) for training associated muscle groups or in muscle isolating forms, such as at use of a bench equipment or apparatus equipment, i.e. a weight machine. Weight training thus gives the advantage of allowing variation of the motion speed in relation to a given resistance even if at higher speeds it will become more uncontrollable and sub-optimated, whereas with pneumatic, hydraulic or expander-based training apparatuses there is a parallel between speed and resistance. The expander-based training apparatus as compared to the pneumatic and hydraulic apparatus, provides the advantage of allowing speed variation at a given resistance, however resistance can be increased only with shortening of the muscle. The expander resistance furthermore is active in eccentric stage of motion, where the resistance decreases at extension of the muscle.
The expander unit thus provides the advantage of variable speed in relation to resistance, which via a possible adjustable transmission (possibly a CAM) can be individually adapted to the force generation of the muscle in different parts of the motion track.
The force generation in a given portion of the motion track is dependent not only of the given resistance, but the biomechanical work moment at a given joint angle gives the prerequisites for its efficiency and decides together with motion speed, the size and direction of the resistance, which of the different muscle fibres or of the motoric units the muscle are engaged.
Not only the selection of engaged motoric units is decided by these factors, but they also influence the proprioceptive nerve functions, ligaments, cartilage and the skeleton structure in different manners.
These conditions are known, but the significance of the direction of the resistance has not been noticed at development of training apparatuses. However, there has issued a patent for a muscle training apparatus, which can be modified to all possible exercises for most skeleton muscles.
This training apparatus, which simultaneously is a computerized measuring apparatus for exercise parameters (motion speed, given resistance and direction of the resistance in all segments of the motion track, etcetera) has a resistance level and direction which can be modified, and a resistance unit, which can be modified (imitating the advantage of the weight unit with inertia and variable speed to the resistance size and eccentric training function).
This training apparatus thus has the ability of stimulating specific motoric units and is therefore useful for training functional muscular force and nerve function.
Beside the fact that this apparatus is big, complex and very expensive it is on the other hand not selectively functional in its training of muscular force, proprioceptive nerve function, ligament function, cartilage function and skeleton function, as it has no possibility of controlling the joint angle/angles of the training person, which angles are engaged in different parts of the motion track, and the selection i.a. of motoric units, therefore vary more from one motion repetition to another than at the joint controlling training apparatus according to the invention described hereinafter.
The importance of the possibility of controlling every factor in the training motion is crucial for development of the very quality aimed at in the shortest and most effective time (muscular strength, coordination, speed, muscular endurance, nerve function). This is of great importance in athletics, but it is at least as important in patient rehabilitation, wherein the physical development today is carried out in integrated as well as differentiated forms (training of every component separately, i.e. muscular strength separately, speed separately, etcetera). Each separate component in differentiated training has specific training requirements for obtaining most efficient development. The development of maximum muscular strength as mentioned requires a high resistance with a few repetitions in the desired neuro-muscular path desired in each joint position. The position of the joint thereby must be arrested for involved joints in order to make the selection of stimulated motoric units as exact as possible, at otherwise unaltered conditions. All differentiated muscular training therefore must be exercised in such a joint controlled manner as possible. As muscles often have a function and therefore extend over one or more joints, and as the force development of the muscle also depends on the initial length of the muscle prior to its contraction it is necessary that the joint angles are controlled during the training motion.
No known training apparatus has the ability of controlling both the joint angle/angles and the direction of the resistance. The training apparatus now sketched is unique in that the selection of stimulated motoric units is better than at any other known apparatus.